The invention relates generally to a system for detecting leaks or unwanted liquid flow in a fluid supply system, such as the plumbing system of a house or building, and means to automatically preclude fluid flow to prevent damage to the structure. More particularly, the invention relates to such a system which is capable of detecting very small volumes of fluid flow, is capable of overriding the shut-off means for a limited time period to allow short term usage of the fluid supply system, and also prevents damage from backflow from the outflow conduit of the fluid system by providing an audible alarm and shutting down any inflow of fluid.
In any building with a fluid supply system, there is a constant danger of damage to the building from failure of the fluid supply system. Houses and most buildings have supply conduits to bring water into the building, a large number of internal conduits to deliver the water to outlets and appliances, a number of internal conduits to remove waste water, and a discharge conduit to deliver the waste water to the sewer system or a septic tank. Any of these fluid supply components can fail, resulting in small or large leaks, and the appliances which use water can also fail and release water into the building. Additionally, a clogged discharge conduit or flood conditions can cause water to back up into the building and overflow toilets or sinks. The amount of damage caused by a fluid system failure is directly proportional to the amount of water flow and the length of time before the failure is detected. If a building is occupied, then an alarm may be sufficient, but an alarm alone still requires the occupant to manually shut down the inflow of water. If a building is not occupied, then an alarm alone is completely inadequate and an automatic water shut-off system is required to prevent what can be extensive damage from even a small leak allowed to flow uninterrupted for a long time period.
Systems have been developed to address some or all of these problems, but none have provided adequate solutions for all possible scenarios in a system which is relatively easy to operate and inexpensive to install. The use in general of flow detectors, shut-off valves and alarms is well known, but previous systems have numerous drawbacks. Furthermore, it is most desirable to provide a system which operates automatically to shut down all inflow of water in a leak situation, even where the leak is very small, but which provides an override to allow for minimal or automatic water usage, such as for hand washing, toilet flushing or refill of an automatic icemaker, without causing activation of the shut-off mechanism.
Examples of prior systems include U.S. Pat. No. 5,004,014 to Bender, U.S. Pat. No. 5,251,653 to Tucker et al., and U.S. Pat. No. 5,409,037 to Wheeler et al. The Bender device is primarily a water use control system, in that the system times water usage and shuts it down after a preset period of time, after which the system must be reset to allow water flow again for the preset period of time. This is not effective protection against pipe failure, in that the system may be (and most likely will be) preset to allow for long periods of water flow, which would be required for washing machines, dish washers, showers, etc. The Tucker device is not useful to detect small leaks, in that it utilizes a flow rate measurement to initiate shut-down with an allowable minimum flow rate to allow icemaker operation. Additionally, this system does not allow for short term regular flow, such as would occur with flushing a toilet. Such an event would trigger the system and shut down all water flow. The Wheeler system is another timer system and is defective in that it will allow a significant amount of water flow prior to deactivating the system.
It is an object of this invention to provide an automatic leak detection and fluid flow shut-off system which is capable of detecting extremely low flow amounts, preventing inflow from the supply conduit when activated, detecting backflow from the discharge conduit, and activating an audible alarm when excessive flow is detected. It is a further object to provide such a system which can be programmed to be operative and non-operative for specific time periods and days. It is a further object to provide such a system which can be programmed to allow flow for a given time period before activation of the alarm and shut-off means for such things as refill of an automatic ice maker, flushing a toilet, washing hands or getting a drink of water.